Safety and efficacy of a Bluetongue inactivated vaccine (serotypes 1 and 4) in sheep

A new inactivated vaccine against Bluetongue virus (BTV) serotypes 1 and 4, was developed from field isolates. Safety and efficacy of the vaccine were evaluated in sheep by serological monitoring and virus nucleic acid detection after experimental infection of vaccinated animals. Seroconversion was observed in vaccinated animals at day 14 post vaccination (pv) with neutralizing antibody titer of 1.9 and 1.8 for serotypes 1 and 4, respectively. The titer increase significantly after the booster reaching 2.7 and persist one year >1.5 for both serotypes. After challenge with virulent isolates, vireamia was recorded in control animals, as evident by q-PCR with threshold cycles (Ct) ranging from 24 to 31 and peaked at day 10 post challenge, while no vireamia was detected in vaccinated animals. Vaccinated sheep were fully protected against the disease and infection.

In-vitro and in-vivo study of the interference between Rift Valley fever virus (clone 13) and Sheeppox/Limpy Skin disease viruses

Viral interference is a common occurrence that has been reported in cell culture in many cases. In the present study, viral interference between two capripox viruses (sheeppox SPPV and lumpy skin disease virus LSDV in cattle) with Rift Valley fever virus (RVFV) was investigated in vitro and in their natural hosts, sheep and cattle. A combination of SPPV/RVFV and LSDV/RVFV was used to co-infect susceptible cells and animals to detect potential competition. In-vitro interference was evaluated by estimating viral infectivity and copies of viral RNA by a qPCR during three serial passages in cell cultures, whereas in-vivo interference was assessed through antibody responses to vaccination. When lamb testis primary cells were infected with the mixture of capripox and RVFV, the replication of both SPPV and LSDV was inhibited by RVFV. In animals, SPPV/RVFV or LSDV/RVFV combinations inhibited the replication SPPV and LSDV and the antibody response following vaccination. The combined SPPV/RVFV did not protect sheep after challenging with the virulent strain of SPPV and the LSDV/RVFV did not induce interferon Gamma to LSDV, while immunological response to RVFV remain unaffected. Our goal was to assess this interference response to RVFV/capripoxviruses’ coinfection in order to develop effective combined live-attenuated vaccines as a control strategy for RVF and SPP/LSD diseases. Our findings indicated that this approach was not suitable for developing a combined SPPV/LSDV/RVFV vaccine candidate because of interference of replication and the immune response among these viruses.

Comparative thermo-stability of two Rift Valley fever virus vaccine candidate CL13T with a recombinant arMP-12ΔNSm21/384

Rift Valley fever (RVF) is a zoonotic, viral disease, transmitted by mosquitoes, characterized by high mortality rates in young animals. RVF is an endemic and enzootic disease in the Arabian Peninsula and Africa, causing public health and economic instability. Therefore, it is important to develop vaccines to minimize outbreaks and combat the disease. We documented the stability of the thermo-stability of live attenuated RVF CL13T and recombinant arMP-12ΔNSm21/384 vaccine candidates at different temperatures, including these vaccine viruses in liquid and lyophilized form. The study revealed that both CL13T and recombinant arMP-12ΔNSm21/384 strains were stable for more than 18 months at 4°C. We show that at room temperatures (37°C and 45°C) the CL13T was less temperature sensitive than MP-12NSm-del in both lyophilized and liquid form. These findings are useful for the preparation of RVF vaccines that will avoid the need for a cold chain and therefore, will improve the application of the vaccines under field conditions.

Peste des petits ruminants pathogenesis on experimental infected goats by the Moroccan 2015 isolate

Background

Peste des petits ruminants (PPR) is a viral disease of major economic importance on small ruminants. Goats are usually known to be more susceptible to the disease. Infection chronology, virus circulation, and the disease early detection need to be better understood. This study evaluates the tissue tropism and pathogenesis of PPR following experimental infection of goats using a lineage IV virus, the most dominant in the world originated from Asia. PPRV infection was experimentally induced in 4 six-month-old goats by intra-nasal and intravenous route of cell virus suspension and from infectious mashed tissue. The clinical signs were observed and goats were euthanized at predetermined clinical score level for post-mortem examinations and PPRV detection by RT-PCR. Clinical signs of infection were present, pyrexia, serous-mucopurulent nasal discharges, coughing, diarrhea and asthenia, for both cell virus suspension and infectious mashed tissue. PPRV genome was highly detected in swabs and tissues with clinical signs dominated by pulmonary attack and digestive symptoms secondary.

Results

Results of this study indicates that PPRV is an invasive infection in animals that in a short period, less than 10 days, invade all vital organs. On live animals, early diagnostic may be easily done on lacrimal and rectal swabs.

Conclusion

The experimental PPRV-infection model using the cell virus suspension is suitable for vaccine evaluation as a standard model.

Safety and immunogenicity of a live attenuated Rift Valley Fever recombinant arMP-12ΔNSm21/384 vaccine candidate for sheep, goats and calves

Rift Valley fever (RVF) causes serious health and economic losses to the livestock industry as well as a significant cause of human disease. The prevention of RVF in Africa is a global priority, however, available vaccines have only been partially effective. Therefore, the objective of this study was to evaluate the safety and immunogenicity of a live, attenuated recombinant RVFV arMP-12ΔNSm21/384 nucleotide deletion vaccine candidate in domestic ruminants. Evaluation involved testing to determine the infectivity titer of the vaccine virus in Vero cells for industrial scale up vaccine production. Safety experiments were conducted to determine the potential of the vaccine virus to revert to virulence by serial passages in sheep, the possibility of virus spread from vaccinated sheep and calves to unvaccinated animals, and the potential health effects of administering overdoses of the vaccine to sheep, goats and calves. The immunogenicity of 3 doses of 10⁴, 10⁵ and 10⁶ Tissue Culture Infectious Doses_50% (TCID₅₀) of the vaccine was assessed in 3 groups of 10 sheep and 3 groups of 10 goats, and doses of 10⁵, 10⁶ and 10⁷ TCID₅₀ was evaluated in 3 groups of 10 calves subcutaenous vaccintation. The results showed that the infectivity titer of the vaccine virus was 10^8.4 TCID₅₀/ml, that the vaccine did not spread from vaccinated to un-vaccinated animals, there was no evidence of reversion to virulence in sheep and the vaccine overdoses did not cause any adverse effects. The immunogenicity among sheep, goats and calves indicated that doses of 10⁴-10⁶ TCID₅₀ elicited detectable antibody by day 7 post-vaccination (PV) with antibody titers ranging from 0.6 log to 2.1 log on day 14 PV with sustained titers through day 28 PV. Overall, these findings indicated that the RVFV arMP-12ΔNSm21/384 vaccine is a promising candidate for the prevention of RVF among domestic ruminants.

Safety and immunogenecity of a live attenuated Rift Valley fever vaccine (CL13T) in camels

Background

Rift Valley fever is an emerging zoonotic viral disease, enzootic and endemic in Africa and the Arabian Peninsula, which poses a significant threat to both human and animal health. The disease is most severe in ruminants causing abortions in pregnant animals, especially sheep animals and high mortality in young populations. High mortality rates and severe clinical manifestation have also been reported among camel populations in Africa, to attend however none of the currently available live vaccines against RVF have been tested for safety and efficacy in this species. In this study, the safety and efficacy (through a neutralizing antibody response) of the thermostable live attenuated RVF CL13T vaccine were evaluated in camels in two different preliminary experiments involving 16 camels, (that 12 camels and 4 pregnant camels).

Results

The study revealed that the CL13T vaccine was safe to use in camels and no abortions or teratogenic effects were observed. The single dose of the vaccine stimulated a strong and long-lasting neutralizing antibody response for up to 12 months.

Conclusion

The presence of neutralization antibodies is likely to correlate with protection; however protection would need to be confirmed by challenge experiments using the virulent RVF virus.